Two-Photon Oxygen Sensing with Quantum Dot-Porphyrin Conjugates

Supramolecular assemblies of a quantum
dot (QD) associated to palladium­(II) porphyrins have been developed
to detect oxygen (pO2) in organic solvents. Palladium porphyrins
are sensitive in the 0–160 Torr range, making them ideal phosphors
for in vivo biological oxygen quantification. Porphyrins with meso pyridyl substituents bind to the surface of the QD
to produce self-assembled nanosensors. Appreciable overlap between
QD emission and porphyrin absorption features results in efficient
Förster resonance energy transfer (FRET) for signal transduction
in these sensors. The QD serves as a photon antenna, enhancing porphyrin
emission under both one- and two-photon excitation, demonstrating
that QD-palladium porphyrin conjugates may be used for oxygen sensing
over physiological oxygen ranges.